FOCUSING-DEFOCUSING OF KEV ELECTRONS ALONG [001]FE AND [101]FE ATOMICCHAINS

We have investigated the focusing and defocusing process of a primary electron wave along Fe atomic chains. To this end, we measured the int ensity of the LVV Auger signal, as a function of the incidence angle o f the primary beam, from a Co him buried in a Fe matrix. We found that maximum focusing efficiency takes place for six scatterers along [001 ]Fe atomic chains, then defocusing starts to set in. However, a signif icant anisotropy is still detectable at eleven scatterers deep in the bulk. The anisotropy depth profile we measured has been used to evalua te the anisotropy in more complex situations, such as thin films and m ultilayers.